Propeller



July 16, 1929. E. A; SCHROEDER 7 PROPELLER Filed July 25, 1927 2- Sheets-Sheet l IN VEN TOR frnesffljc/vroeaer WWW A TTQRNEYS July 16, 1929. A SCHROEDER 1.720,969

- PROPELLER Filed July 25, 1927 2 Sheets-Sheet 2 F I [:5 -E- y A TTORNE YS Patented July 16, 1929.

UNITED STATES,

ERNEST A. SCHROEDER, OF SAN FRANCISCO, CALIFORNIA.

PROPELLER.

Application filed July 25,

My invention relates to propellers particularly adapted for use on aeroplanes and is concerned with propellers of the feathering blade type.

Feathering blade propellers for aeroplanes have been employed in the past and while such feathering propellers give good results,

they do not produce the highest efficiency and it is therefore an object of my invention to increase the efficiency of a feathering blade propeller.

Another object of my'invention is to provide a feathering blade propeller in which the speed reduction gearing for the actuating shafts is contained in the hubs of the blades.

Another object of my invention is to vary the slope of the blades of the propeller with respect to the cycloidal path followed thereby.

My invention possesses other advantageous features, some of which with the foregoing will be set forth at length in the following description where Ishall outline in full that form of the propeller of my invention, which I have selected for illustration in the drawings accompanying and forming part of the present specification. In said drawings I have shown one form of propeller embodying my invention, but it is to be understood that I do not limit myself to such form since the invention, as set forth in the claim may be embodied in a plurality of forms.

In the drawings Fig. 1 shows the feathering propeller of my invention as seen from one end, portions of the mechanism being disclosed in cross section.

Fig. 2 is a section of the propeller hub, the plane of section being indicated by line 22 of Fig. 1.

Fig. 3 is a diagrammatic representation of the path of a blade of a. feathering propeller showing the effect of concentric gears. I

Fig. 4 is a diagrammatic representation of the path of a blade of my propeller showing the effect of eccentric gears.

In its preferred form, the propeller of my invention preferably comprises a plurality of feathering blades adapted to follow a cycloidal path and provided with mechanism whereby each blade in most positions is afforded a slope different than the usual slope of a blade in those positions on a cycloid.

In the embodiment of my invention disclosed in the drawings, I preferably provide a plurality of propeller blades 6 usually dis- 1927. Serial No. 208,385.

posed transversely of an aeroplane and mounted on suitable axles 7. Each blade preferably comprises a relatively rigid frame 8 which is covered with flexible material such as fabric 9. Each of the blades usually is generally rectangular in outline and is. pivotally mounted at each end by means of the axle 7 in a framework 11. Usually a framework is provided at each end of the plurality of blades 6 but inasmuch as the frameworks are similar, only one of them is illustrated and described. Each axle 7 is journaled in, a housing 12 tightly fitted on the end of a radius tube 13 extending from a central hub casing 14. The hub casing is mounted to rotate and in the present instance supports four radius tubes 13 for the four blades 6.

Means are provided for regulating the inclination of the blades 6 as the framework 11 is rotated. The casing 14 is preferably split on a central plane and is provided with a boss 15 rotatively mounted in the frame of the aeroplane. Passing axially thru the boss 15 is a stationary shaft 17 which carries on its end within the casing a stationary spiral gear 18. Meshing with the central gear 18 and having their axes at right angles to the axis thereof are four spiral gears 19 situated within the casing 14 and preferably having a diameter equal to the diameter of the stationary gear 18. The gears 19 are mounted on shafts 21 extending to the housings 12 and are journaled in bushings 22 secured in the casing 14. Preferably, the two halves of the casing 14 are secured together by bolts 23 which also clamp the radius tubes 13 in place. The tubes 13 usually are stream lined to reduce the wind resistance and at their outerends are socketed in the housings 12. If desired suitable bracings or guy wires 24 can be arranged between the tubes 13. The shafts 21 carry at their outer extremities spiral gears 25 which mesh with suitable spiral gears 26 affixed to the ends of the axles 7. 25 and 26 are suitably enclosed by the lions ings 12' and are arranged'so that the axles 7 are rotated at half the speed of the shafts 21. I11 Fig. 3- it will be seen that in ordinary feathering propellers, a typical blade 6 fol-' lows the cycloidal path 27 and in all positions of the blade except the uppermost intersects the cycloid. In the upper half of the cycloidal path, wherein little forward propulsive effect is obtained, the blade offers considerable resistance to movement through the air as it deviates considerably from a tangent to These gears the cycloid. 1n the lower half of the path, the blade does not exert its maximum forward propulsion until it has gained its lowermost position. This becomes apparentwhen it is reinen'ibered that with the two to one reduction of gears and 26, when the framework 11 has rotated a quarter turn, a blade 6 turns from horizontal position to a position making an angle of if) degrees with the horizontal. This deviates from a tangent to the cycloid 27 by an angle or. At this point, angle at varies from zero degrees when there is no slippage of the framework 11 in the air, to T5 degrees when there is 100 per cent slippage. In Fig. 3 it will be seen that with the 50 per cent slippage illustrated, 0c increases from Zero de grees at the uppermost position to twentytwo and one-half degrees at a quarter revolution of the framework.

I preferably provide means for varying the rate of feathering of the blades 6 so that each of them is tangent to its respective cycloid in the upper half thereof. The blades thus present a minimum resistance to movement through the air and the exiicieney of the propeller is increased. Instead of being concentric, the gears 18 and 19 are preferably eccentric, as disclosed in Fig. 2. tricity is proportioned to the slip for which the propeller is designed and in the present instance accelerates the rotation of the blade the first half of the descending portion of the cycloid so that the angle on is zero during the quarter revolution of the framework 11 bringing the blade from uppermost position.

The path of the blade is then still the same cycloid and the plane of the blade is tangent thereto, as shown in Fig. l. The covering of The eceenthe blade, being flexible, generally conforms almost exactly to the cycloid.

During the next quarter revolution, the eccentric gears continue the acceleration of the blade but in decreasing amounts so that in the lowermost position of the blade it is normal to the cycloid and angle on is 90 degrees. The forward propelling component of the blade is thus increased over the usual amount and the propeller efficiency is correspondingly augmented. he final two quarters of the revolution of the framework cause the eccentric gears to impart a negative acceleration to the blade rotation and the blade occupies symmetrical positions on the ascending portion of the cycloid. It is again tangent at the beginning of the fourth quarter revolution with on again equal to zero degrees, and remains tangent to the cycloid with or constant at Zero degrees until the uppermost position is again reached. The cycle is then repeated for each revolution of the framework.

lVhile it is possible to use other means for effecting the desired variation in the slope of the blade 6, T preferably utilize the spiral eccentric gears as shown. The entire assembly produces a very efiicient propeller which is smooth running andhaslong' life.

I claim:

A propeller comprising a feathering blade adapted to follow a cycloidal path, and means including eccentric gears for varying the slope of said blade with respect to said path.

In testimony whereof, my hand.

I have hereunto set nnansr A. sonnonnnn. 

